It is known to produce tin from tin salts, e.g., stannic chloride, in an electrolytic or a divided cell (divided by a permeable, e.g., asbestos or glass fiber diaphragm) using an acidified stannic chloride electrolyte or by introducing a stannic chloride solution into the cathode compartment of the cell and a hydrochloric acid or sulfuric acid solution into the anode compartment of the cell. When direct current is imposed, tin metal is deposited on the cathode. See, for example, U.S. Pat. Nos. 2,250,843; 2,253,865; 1,124,315; 883,139; 883,141; 704,675; 699,012; and 874,707.
Electrolytic cells using a porous diaphragm, e.g., an asbestos type diaphragm, permit the flow of electrolyte solution from one electrode compartment to another which flow may cause contamination. In addition, such cells have low current efficiencies and relatively low yield of tin metal.
In contrast to known fluid permeable membranes, ion permselective membranes, also referred to as ion exchange membranes, have been found useful in a variety of fluid purification applications. One specific use is the demineralization of water. Other specific uses include the treatment of pickling liquors to produce sulfuric acid and electrolytic iron, the treatment of copper or leaching solutions to produce hydrochloric acid and copper and the purification of aluminum sulfate solutions by electrolytically depositing iron therefrom. See, Industrial & Engineering Chemistry, Vol. 54, No. 6, page 29 (June 1962) and U.S. Pat. Nos. 3,537,961, 3,347,761 and 3,787,293. In addition, cationic permselective membranes have been disclosed for use in processes to produce stannic oxide sol products (see U.S. Pat. No. 3,723,273), anionic permselective membranes have been disclosed for use in a process to form tin and lead salts, e.g., stannous sulfate (see U.S. Pat. No. 3,795,595), cationic permselective membranes have been suggested for use in the regeneration and recycling of chromium etching solutions, see Chemical Engineering, June 4, 1979, page 77, and cationic permselective membranes have been disclosed for use in a process to form stannous salts from stannic anions (see my copending application Ser. No. 48,829, filed June 15, 1979).
A number of the known uses for tin and/or tin salts result in the formation of residual tin-containing values such as, for example, glass plant sludge, blue sludge, detinning mud, spend plating baths, spent catalyst systems, drosses, ores, ore residues and the like, which contain not only tin but disparate other metals and/or organic impurities. Since the price of tin has continued to increase, these residua have become increasingly more valuable. While numerous attempts have been made to economically recover the tin values therefrom, most if not all of the attempted processes have been expensive, cumbersome or have relatively low yields.